The Virginia Regimental Histories Series is a good place to start; the book on the 11th Virginia regiment was written by Robert T. Bell. You may be able to also find the civil war diary of William H. Morgan of Company C, which used to be online. Confederate Military History, Extended Addition (the volumes on Virginia and West Virginia) has a lot of interesting biographic information on soldiers of the 11th. As Capt. Robert W. Douthat recalled in Confederate Veteran magazine (vol. 36, p. 61), in early 1863 the 11th was at the siege of Suffolk while the division "was gathering all the bacon out of North Carolina, preparatory to the Gettysburg campaign." Kemper (1823-1895) was a Virginian of the highest character and there is bound to be considerable information available on him, whether online or in basic references such as The Civil War Dictionary by Mark M. Boatner III. I do not know Col. Joseph Mayo, Jr.'s connection to the 11th, but when the Gettysburg campaign began in June 1863 he led the 3rd Virginia Infantry in Brig. Gen. Kemper's brigade.